Reflex-reflecting sheeting



June 22, 1965 MCKENZIE 3,190,178

REFLEX-REFLECTING SHEETING Filed June 29. 1961 3,190,178 a REFLEX-REFLECTING SHEETING Eugene L. McKenzie, North St. Paul, Minn., assignor to Minnesota lVIining and Manufacturing Company, St.

Paul, Minn., a corporation of Delaware 7 Filed June29, 1961, Ser.'No. 120,680 5 Claims. (Cl. 88-82) Thisinvention relates'to beaded highbrilliancy reflex-reflecting sheeting effective as a reflex-reflector of.

light under all weather conditions, thereof is wet or dry. 7 p

The invention further relates to a novel method for making the beaded reflex-reflecting sheeting hereof.

Reflex-reflection of light has now cometo be awellrecognized concept referring to the ability of a surface to return light back toward its source even. though the incident beam may strike the surface atian angle other than normal. Particularly efiicient beaded reflex-reflectors of the high brilliancy? type are disclosed and claimed in Gebhard etal. US. Patent No. 2,326,634, here incorporated by reference. Characteristically, these structures contain a layer of lens elements exposed to an interface of air, with the lense elements preferably having a refractive index 0%) between about 1.7 and 2.0 maximum reflexive light return. An unfortunate drawback of high brilliancy air-interface exposed-lens structures, however, has for years been the fact that reflex-reflective light reurn is blanked out. whenthe lenticular surface of exposed lenses is covered with water.

A solution to the problem of preparing beaded reflexwhether the surface 3,190,178 Patented June 22, 1965 at the same time maintaining maximum exposure of beaded reflex-reflecting complexes for the reflex-reflecting function, has heretofore remained an unsolved problem.

It, of course, is old to place a transparent cover film or plate over the lenticular surface of beaded exposed lens-type reflex-reflectors; and such an expedient is discussed in Palmquist et al. US. Patent No. 2,407,680.

A transparent cover film or plate does not alter the lens action of the beads of an exposed-lens structure, since the'beads still contact at their'front surfaces andthus no interference with the refraction of light at each front bead surface is created. Sealing of the edges of such structures has heretofore been difiicult to accomplish without uncontrolled interference with the necessary exposed-lens feature. Even assuming the edges of such a structure are sealed satisfactorily, one still is left with a sheet article which cannot subsequently be cut as desired into a different shape for sign use, except by destroying edge-seals andmaking it necessary, to seal the cut edges anew. Should satisfactory edge sealing under field conditions be accomplished, resultant shaps for sign use are nevertheless relatively easily rendered useless if punctured ever so slightly during application to a sign base,

reflectors which are effective to return light. toward its source even thoughthe incident beam may strike the surface at angle other than normal, whether the surface of the structure is Wet or dry, is set forth in Palniquist et al. Patent No. 2,407,680. Whileithe Palmquist et a1. teaching is very effective to provide brilliant ,reflexereflection of light under wet or dry conditions, the maximumbrih' by such constructions, and having the ability to serve as a durable high brilliancy reflex-reflector under a variety of weather conditions, regardless of whether or notv the cut sheeting is dry or covered with afilm of water, or even immersed in water. In terms of light return, all

over the area of the reflecting material.

suggested by Hodgson, Jr. et al. for accomplishing this or if punctured atrany time later by vandals. As will further be'explained below, a path for moisture to enter between a cover film and an underlying layer of airexposed lens elements leaves one with a sign element quickly rendered worthless in practical useapplications.

In the recently issued Hodgson, Jr. et :al. U25. Patent No. 2 ,:94 8, 1 91,it issuggested that a" transparent cover filmiover allayer of exposed lenses or beads of a reflex: reflector should be maintainedin fixed relationship to the reflecting material of thereflectoras well as out of contactlwith thebeadlens elements of the structure by meansofa plurality of anchoring points distributed One means I is that of using a plurality of spaced apart beads of somewhat larger size than theibeads relied" upon for lens action in the structure, and anchoring the cover film to .the spaced apart larger beads in the layer. This expedient, of course, serves solely to elevate the cover film.

abovethe beaded lens elements of the structure in a seatsheet products of the invention exhibit a brightnessof light return, as measured by a photometer, at least 400 times greater than that light return from a conventional white paint film. Products having .protometer readings in excess of 1,000 times that for a white paint have been formed according to the teachings hereof.

The sheeting hereof contains a plurality of hermetically isolated groups of exposed-lens-type reflex-reflecting complexes occupying near maximum optical surface area of the sheeting. This sheeting may be cut to various sizes 'by sign converters without disrupting more than a frac- I tional area of the reflex-reflecting complexes along edge portions of the cut. The structure of my sheeting includes a transparent cover film hermetically sealedover the frontface of an exposed-lens sheeting according to a pattern which serves to encapsulate and isolate the exposed-lens portions of discrete groups of beaded reflex-reflecting complexes from other groups thereof in 7 the exposed-lens structure. unsightly or erratic flooding of the exposed portions of beadsror spheres of the exposed lens structure, while.

Accomplishing this without to an interface of air. I of about 2.3 to 2.7 are needed for reasonably efficient tered point fashion without in any way protecting the lens elements from. contamination with water, which latter rwouldvinherently seep between the cover film and lens elements from edge portions of the sheeting in the event of rain, and remain entrapped for relatively long periods thereafter because of capillarity. Varying degrees of moisture contamination underneath the cover film of such structures also occur during the usual change of conditions taking place from daytime, where higher temperatures prevail, into nighttime, where lower temperatures and higher humidity prev-ails and water condensation is apt to occur; and this at the very time reflexreflection of high brilliancy is most critically necessary.

Once contaminated with water, the reflex-reflecting function of air-interference exposed-lens structures is essentially blacked out, inasmuch as the difference in refractive index between water and that of the sphere lenses or beads of the layer in insufficient for effective light return where-the beads of the layer have a refractive index as necessaryfor brilliantlight return when exposed (Beads having a' refractive index reflex-reflection where their surfaces are covered with water, whereas beads between about 1.7 and 2.0 refractive index give best results when exposed to air.)

Another means suggested in the Hodgson, Jr. et al.

patent for creating a number of anchoring points to maintain a transparent cover film inrfixed relationship of the pocket cut through) susceptible; to moisture inter-;

. Referring now to FIGURE 2,.thestructure of my sheetso cut leave essentially ing includes a transparent cover film 12', a layerof'trans parent. small glass beads 13 (e.g,, microspheres) with underlying reflective means 14, a binder layer 15, afurther binder layer 16, and a release carrier 17 underlying binder layer 16. In addition, a critical part of the structure of the sheeting lies in the. narroW-line-area of the hermetic seal 18, where the binderinaterial from layer 15 forthe beads in other portions of thesheet structure,:and

any intermingled material from layer 16, is actually forced into intimate hermetically-sealed contact with thetransparent cover film 12. The small glass beads in the pattern of hermetic seal throughoutjthefsheeting are charsuch as silver, aluminum, etc.

acteristically flooded over and masked by binder material.

in which the glass beads of other areas of the sheeting are; partially embedded. l If desired, a layer of pressure-sensitive or other suitable adhesive may be applied'to the rear'surface of the sheeting, together with a removable interliner.

The preferred transparent cover film 12,for.the sheetin is a film of biaxially-oriented methyl metha'crylat'e.

Methyl methacrylate is highly resistant to theefiects of sunlight exposure, rain, snow,sleet, thermal shock and fungus growth. Biaxial orientation converts thin films of this material from a brittle, egg-shell state into aflexible state of good strength and handling properties. The bi-. axially-oriented material is particularly useful in the range of about 1 or 2 mils thick up to about 5 mils thick, where its moderate strength properties, handleabilityand flexii bilityareespecially desired in combination with its resistance to crazing, cracking and discoloration. A suitable method for forming thinbiaxially-oriented methyl meth acrylate films is that of extending a 12-15 mil thick sheet of methyl methacrylate at about 5 00 F., and then stretching the film biaxially in tentering equipment at temperatures of about 270". P. so. that thefinal-film isabout 3 I mils thick and, about two and one-half times as long and about two and one-half extruded material. p

If desired, other smooth, essentially-uniformly thick, self-supporting, transparent films such as, for example, polyethylene terephthalate (Mylar), cellulose acetate,

cellulose acetate butyrate, etc., may be used in place of the preferred film of biaxially-orientedj methylmethacrylate. without departingfrom the. essential structural features of the invention; however, such substitutefilms are much less durable than biaxially-orientedv methyl methacrylate films and for this reason give products having a relatively short useful life as compared to products made where usingthe preferred transparent cover layer.

f While transparent coverfilms no greater than 5 mile thick are preferred, the structural features of the invention, except for sacrifice of flexibility, are largely retained even when transparent cover films or sheets as thick as 10 inils or even 20 mils are employed; The most useful thickness for cover films is between about l -and 5.mils.

adequate strength and handleability. I

Transparent cover films may be colored or even may consist of a laminate of materialswith or without one. layer of the laminate containing transparent color..pig-

mentation.

. Smallglass beads 13 for the structure should not exceed times as wide as the. originally about'200- microns diameter and preferablybe no larger than about 75 microns diameter. They may be as small as about 10 or 15 microns in diameter, although such very small glass beads or microspheres are diflicult to manufacture. Between about 25 and 75 microns diameter best results are gained. The refractiveindex'of the beads, of course, shouldrest within the limits of about 1.7 to.2.0, since the compactmonolayer of beads is, except for the hermetic seal pattern, exposed to air media in the final structure; i h 7 As illustrated in-FIGURE 2, internal light reflecting means 14 underlie thebeads in the structure in opticalconnection with the back extremity thereof. Suitable underlying reflecting means of the specular type, as preferred, may consistof uniformly-thick metallic deposits As in the teaching of US. Patent No. 2,326,634 to Gebhard et al., the beads of the structure in all areas of'reflex-reflection are partially embedded in a binder layer 15, which suitably may be an organic resinous mate of thefinal. product should not flow. at temperatures below about 150 E, where the final product is to be used inapplications exposed to solar heat, By employing color pigments in the binder layers, particularly optically exposed-binder layer 15, improvements in the attractiveness of the external or face appearance of the reflex-reflector may be gained. Thefundamental purpose of binder layer 16, sometimes herein referred to as a cushion layer, is that of providing an adequate mass of material, in combination with binder layer 15, for" enveloping glass beads in those limited line pattern areas where a hermetic seal'to the cover film is to be accomplished. The material of binder or cushion layer 16 may consist of the same material as that in binder layer 15; but it preferably is a material which exhibits sufiicient flexibility at the thicknesses employed so as to remain unbroken or uncracked in 'final flexible sheet articles. Heating of limited portions of the binder layers during formation of the hermetic seal pattern serves to convert the binder layers into a viscous fiowable state so that pressure applied thereto will force such material between glass beads in the limited pattern of hermetic seal and into contact with the interior surface of the transparent cover film Where a vandal-resistant firm' and permanent hermetic bond is formed.

Since the function of the carrier material 17 is essentially that of serving as a low adhesion or release surface to which the pattern of a heated embossing die used in manufacturing the sheeting will not stick, any of a wide variety of materials may be used as a satisfactory carrier film. For example, such materials as polyethylene terephthalate (Mylar) films, cellulose acetate butyrate, polycarbonate, vinyl butyrate, etc. are suitable. Indeed, if desired, the carrier film 17 may be omitted from the structure, and the problem of die sticking avoided by employing 'a low adhesion silicone coating over die elements pressed into contact with portions of the cushion 7 v V be observed by reference to FIGURE 3, die elements 19, Such films provide mm'mum flexibility consistent with member 20, preferably not heated and suitably covered means withrubber so .as to permit yielding without lossof the 7 moderate pressure needed. forv hermetic heat-sealing according .to the patternof the dieelements. The die V "elements are heated sufficiently and pressed against the rear surface of the,laminatelongenoughgto cause heat fluidization and viscous displacement of binder material toward the cover film 12'. Temperatures used for the die element and the time ofpressing them against the binder;

material may therefore vary greatly, and are governed by the temperature at which binder material fluidizes sufficiently "to -move into contact with and sealto the cover film as well asthe time afterinitial' die contact. a

Generallyjthe thickness of binder 1ay ers and 16 should at least about equal the average diameter of the glass beads employed in thestructure andrnay approach up to about 1 /2 or even 2--or possibly 3 times the'diam;

eter of thebeads employed in the structure.

Where the transparent cover 'film selected is one does notdeform orwarp o'r degrade under the temperarequired toreaich such condition cording to the preferred processhereof. 7 Transparent glass beads having anapproximate diam eter from to 65r'nicrons and a refractive index of 1.92]

ture conditions required'for a hermetic line-seal format 7 tion, it is suitable to accomplish lamination" along the intersecting grid lines without taking special precaution to. prevent'the transparent cover film itself from reaching the temperatures required for the formation of a. heat-seal hermetic bond.'- However, Where uncontrolled heating of the transparent-cover film occurs, danger also arises that portionsof the binder orfbead-bond coating adjacent lines'of heat-seal may become fluidized' toi the point'where'it flows out of'place and'disrupts the desired reflex-reflection performance of beads in such areas.

Thus, by far the most beneficial results of the-invention are gained when network lamination of the cover film and I underlying reflux-reflecting structure .is accomplished by pressing a heated embossed die against the deformable" layers of the structure underlying thevglass bead layer. thereof while maintaining the transparent cover. film in such'areas incontact with a non-heated or evien cooled surface. n

Another point to keep in'mind fis.that cover films which exhibit even some thermoplasticity at'the interface contacted with bead-bond material'during thestep. of heat-sealing are preferred in, that a stronger'heat-fusion generally smooth front face for the' sheeting hereof; and properly so since this feature aifords several advantages 7 when considered with. other characteristics of the structure. Fine silk screenprintingmay be accomplished over a smooth front facefor the sheeting, which makes for.

versatility of use for the structure in signs. -A smooth surface is easily wiped clean, whereas a rouglroneis .most difiicult toclean. However, where aifron t surface need not be so smooth as to permit silk screen printing of the. finest character, andyet theirregularitiesof the surface are to. be controlled so as to avoid crinklingfor crepe-like, surfacing, it is quite within the scope of the i 8'6; .1 t ample of a preferred sheeting of the invention-formed acare temporarily bonded in a polyethylene coatingon kraft paper. (the. polyethylene coating on the paper being at .a quantity of about 18 pounds per ream of 60 'pound wet strength kraft paper) In accomplishing this temporaryr bonding, thepolyethylene coated paper, with itscoated f side' outwardly, is passed overthe. surface. :of a drum heated sufficiently to cause thepolyethylene to become] v tacky. V SimultaneouslyJhe heat-tackified coating of polyethylene is dipped into contact with a mass ofthe glass beads in a trough beneaththehotdrum. The tackyplastic coating causes a compactmonolayer of glass headstol be picked'up. Then thepolyethylenecoating is heated sufliciently .to cause the polyethylene to soften andpartially draw intoitthe compact monolayer of beads to T 7 approximately 40 to.45%. ofgtheir diameter. (e.g., about '40 to of total-bead surface). The structure is then cooled; suitably by blowing room temperature air thereover.r; a r y Over the projecting'beads of the, polyethylene layer. is

then squeeze roll coated a bead-bond. coating consisting of a solution. Qf'3, partsby weight 'of a solid thermoplastic film-forming methyl methacrylate polymer material (AcryloidB-72: of Rohm &Haas), with 3 parts pigment graderutile, in 3 parts'toluene and sufii'cient Xylene to thin viscosity to about 4QO cps.. This coating is applied .at a wet 'weight of; about .4 grains per 24 square inches,

after which solvent is evaporated by passing forcedair at Hover the surface; V

- i Thenxthe bead-bond, coating is buffed withja felt. or 100% wool and about inch thick to remove bead-bondfrom the. outermost areaof the spheres (i.e., the'outer approximately 20% ofthe totalJarea thereof).

" Aluminum is then vapor-coatedover the exposed sur-& face of the structureuntil a specular visually continuous coating'is formed. The exposed 20% or soof the beads A .as well as the exposed, surface, of the bead-bond coating are thusrefiectorized.- I a I Thereafter, ;over:the aluminumcoating, is applied a cushion binder coating consisting of the following comi position: About 25 parts by weightgof thesolid thermo- 1 plastic film-forming methyl methacrylatepolymer used inthebeadwbond coating, 25 parts pigment grade rutile, 6

parts of a solid thermoplastic film-forming ethyl acrylate polymer. (CIOLV of Rohm & Hass), 6 parts of epoxidiz'ed? soybean 'oil plasticizer (.Paraplex 'G -62' of Rohmf& 1 Haas), and'34 parts toluene. This compositionis applied at a coating weight sutficient to give adry film. of about 2 to'4 milsthick over the aluminum coating, after which 1 solvent. is. evaporated from thecoating by forced air drying at -F. n

A 'stretch-resistant film which does not become tacky at 'the temperatures of .thermoplasticity for vthe cushion coating is then applied thereover. The film. suitably is polyethylene .terephthalate coated with about a 0.5 mil thick; layerof' methyl isoamyl acrylate (apressure-sensL broad concept hereofto accomplish hennetic sealing along intersecting lines by using coacting die elements opposite those applied against the rear surface. of the sheet strucf ture (and identicalin .configuration'to those applied against the rear surface) and to apply heat from die elements on one or bothqsides of the loose laminate duringhermetic sealing; Also, if desired, a flat back-up surface may be used where heated network die elements are applied over the cover film surface to accomplish line' sealing.

i Thefollowing is'ofiered as a specifiic illustrative .ex-r

tive adhesive) for adhesion to the cushion coating;

The entire structure so formed is stripped'from the polyethylene.coatedpapercarrier, andlthen placed'with its ex posed'bead surface in loose contact with a 3 mil thick bi-.

axially-oriented methyl methacrylate film. The two layers 1 of the composite article-are passed at the rate of about 10 feet per minute between a metalembossing rollheated to about 270-300 F., and a non-heated rubberroll, with the 'biaxially-oriented methyl methacrylate; film in con- 'tact with the non-heated rubber roll. The embossing of the metal rollsuitablyis that of intersecting. lines in a grid pattern with /iin'ch'l square open recesses defined by V intersecting inch wideflines of the pattern. The nip between therolls'is adjusted so that the twolayersof the. compositearticle are subjected to justsufiicient pressure to cause material .of the binder layers'of the. structureto 1' 9 move into firm hermetic, bonding contact with the cover film according to the limited die contact pattern under the temperature and time conditions employed,

The cushion coating of the illustrated structure softens and flows at about 200 F.; and the bead-bond layer soften and flows at about 280 F.' During lamination along lines of the grid pattern, thecushion coating'and compatible material of the bead binder layer 15 apparent- 1y blend together on their way to the transparent cover film. No tearing of the beaded structure of the-laminate occurs; and indeed, the beads in the area'of displaced binder material appear to remain essentially in the same plane as the beads in other areas. They, of course, become .flooded or swallowed by the flowing binder material in the limited areas of seal, which results in destruction of reflex-reflectivity in those limitedareas. It is significant, however, that squashing or flooding out of bead-. bond material into areas of the structure other than the line areas of seal is controlled and prevented by the steps of the heat-sealing process incombination with the structural features of the product sealed.

. As an incidental observation, the aluminum deposited on the bead-bond layer between the glass beads in the area of the line seals is disrupted in those areas during the formation of the hermetic line seals. This is not objectionable. (Of course, where hemispherically metallized beads are oriented in the reflex-reflector, without metal deposits underlying portions of the binder layer 15 between beads, such displacement of metal deposit as dis cussed for the preferred example "does not occur during hermetic line sealing.)

During passage of the exposed-bead structure and cover film between the rolls, suificient heating of the bead-bond coating occursto effect heat fusion of that coating to the biaxially-on'ented methyl methacrylate cover film in the mannerofheat-seal connection; but the outer surface of the biaxiallyoriented 'methyl methacrylate cover film usually should not be raised above about 200 F., prefer- 7 under daytime conditions as well, as exhibits brilliant rei flex-reflection under nighttime conditions. Between exbe sealed along its cut edges (cut to form letters or other characters), when adhering it to a rigid sigml gase of thesame size andshape, by using a vacuum and heating technique as described in Douglas US. Patent No. 2,620,284.

" Another advantageous feature of the preferred sheeting illustrated is ,that it presents an attractive-appearance posed beads of the structure illustrated in,the drawing is a pigmented binder which is optically in association with the beads,'except.for a small underlying'specular reflective cap on each'bead of the layer. Light from the. sky

striking theface of the structure is therefore somewhat diffused in its'treflection so :that an observer not in line with the incident light receives at least a'portion of that lightzand gains a favorable impression of coloration. At the same time, an observer in line with incident light gains brilliant reflex-reflection as desired. Where :beads of a. layer are all equipped with'hemispherical specular-refiectingcaps between which the binder is pigmented, incident 7 light is brilliantly reflex-reflected but the reflex-reflecting: complexes of the layer act more aslight traps inthat they lack the ability to diffuse incident sky light asdescribed for the preferred structure hereof.

'In addition to noted performance features,.the product exhibits a reflex-reflecting light return significantly approaching that return exhibited by an otherwise identical sheeting free of the cover film and free of the intersecting grid pattern of flooded and encapsulated beads. Specifi cally, the reflex-reflecting light returnfor the preferred product illustratedis at least two-thirds that exhibited by 7 an otherwise identical sheet free of cover film andlines of the hermetic seal; but the product of the invention does,

7 not become blacked out under conditions which render ably not above about 180 F. It is important, when making the preferred structure here illustrated, where a biaxially-or iented methyl methacrylate cover film is employed, to maintain the film at a temperature below its reversion temperature, which generally means that the temperature of the outer surface of the film should not exceed about 200 F. Above about 220 F., biaxiallyoriented methyl methacrylate films tend to shrink and unsightly results ensue. ThereforeQthe biaxially-oriented methyl methacrylate film, during the step of sealing, should be maintained in contact with a relatively lower temper- V ature surface. If'necessary, the surface should be artificially cooled so as to prevent its temperature from rising to the point where heat from the heatedmetal embossing roll is sufficient, in combination with residual heat of the rubber roll, to' elevate the temperature of the biaxiallyoriented methyl methacrylate to the point of causing it to shrink or crinkle.

The product prepared as specifically illustrated has the over-all thickness of about 11 mils, and a front face appearance as shown in FIGURE 1, with an intersecting network of hermetic seal line areas between its transparent cover film and its network-displaced bead-bond coating. When placed in water and the atmosphere thereabove subjected to vacuum-pressure cycling for 25 cycles (25 inches of mercury for 15 minutes followed by 19 psi. gauge pressure for 15 minutes), it stood up with no water penetration into its hermetically isolated pockets of air-exposed reflex-reflecting heads. when subjected to 25 cycles of hot-cold cycling (15 minutes in 140 F.-water followed by 15 minutes in 32 F. water), it stood up without failure, i.e., without water penetration into the hermetically isolated pockets. It has been subjected to elevated temperature conditions for lengthy periods, to tropical conditions of high relative humidity and varying high the latter sheet material worthless as a" reflex-reflector; That which is claimed is: n ,r 1. Reflex-reflecting sheeting comprising a continuous layer of glass beads in compact relationship to one another, and means separating said layer of beads into a plurality of discreteencapsulated and'hermetically sealed;

pockets having no lateral dimension greater than threefourths inch, with. the beads of eachsaid discrete pocket,

optically exposed to an airinterface, said separating means,

being relatively small in total area as compared to the total area of said pockets, and said separating means including an intersecting grid pattern of pressure-formed heat-sealed connection between the structure of said reflex-reflector overlying said layer of beads and the structure of said reflex-reflector underlying said layer of heads, the structure overlying said beads comprising a transparent cover film, and the structure underlying said beads comprising a binder layer in which said beads are partially embedded and internal light-reflecting means underlying said beads and in optical connection with the back extremities thereof, those beads of the sheeting in the intersecting grid pattern of pressure-formed heat-sealed connection being flooded over and optically obscured by V binder layer material displaced from said binder layer and hermetically sealed to said transparent cover film according to said intersecting grid pattern.

2. Reflex-reflecting sheeting comprising a. continuous layer of glass beads in compact relationship to one another and with underlying reflective means associated therewith, a transparent cover film overlying said layer of beads and unattached to a major portion thereof, a binder layer in which those beads of said continuous layer unattached to said cover film are partially embedded, and means separating said continuous layer of heads into a plurality of discrete 'encapuslated and hermetically sealed pocketshaving no lateral dimension greater than threefourths inch, said separating means being relatively small total area of said pockets,

pockets being optically obscured by part of the means t which separates said continuous layerofibfeadsinto-a plu-' rality of pockets, said means "including an intersecting gridpattern of pressure-formed heat-sealed connection between-said overlying transparent coverfilm and material displaced from said-binder laye'r and hermetically sealed in contact with said cover film between said pockets of beads I 7 t t 3'. Flexible reflex-reflecting sheeting of; the high-bril-, liancy air-interface exposed-lens type comprising a base structure and atransparent cover film-overlying and her-- meticallysealed to said-base structure according to' an in-' tersecting grid pattern forming a plurality of discrete airfilled pockets over the face of said base structure, said I discrete air-filled pockets being such. as to not exceed three-fourths inch in lateral dimension, the total area of hermetically sealed grid pattern beingrelativelysmall as e compared to the total area of said discrete air-filled pockets, saidbase structure comprising a compact layer of glass beads, internal specular light-refiecting means underlying said beads, and a thermoadhesive binder layer in which beads of the base structure located-in the aforesaid 7 pockets are-partially embedded, and in which beads of the base structure located inthe aforesaid intersecting grid pattern are fully'embedded and optically obscured, said intersecting gridpattern of said sheeting being formed by material dipslaced from said binderlayer and hermetical- 1y sealed to said transparentcover film according to said grid pattern.

" =4. RefleX-reflecting-sheeting comprising a transparent cover film, a plurality ct -discrete reflex-reflecting pockets of air-exposed glass beads in a monolayer with-associated underlying reflective means located behind said cover film,

a binder layer in which glass beads of said pockets arepartially embedded and towhich said transparent cover film is hermetically sealed according to an intersecting,

grid pattern between said' discrete reflex-reflecting pockets,

structure being relatively small as compared to'the total area of said discrete reflex-reflecting pockets, the interthe lateral dimensions of saiddiscrete reflex-reflectingpockets being not in excess'of three-fourths'inch, with the total area of the hermetically sealed 'grid pattern of said 45 secting grid pattern of hermetic seal between said cover to saidigrid patterii.

, 5'. Reflex-reflecting sheeting :compr-isifig a continuouslayeri of glass, beads} in compact ,rlationship to one? anv other, and means se'parating said; layer of beads into a pine ralit'y erdiscrete encapsulate'diand hermetically sealed" pockets having' no lateral dimension greatertl la n three fourths lHClL'Wlth' the beads of each said discrete pocket" optically, exposed to an air-- interface, said separatingmeans being relativelysmall in total area as compared-t0;

the total area of said pockets and said separating ineans including-anintersecting grid pattern of pressure-formed l'i eat-sealed-connection between-j be structurejof said re, flex-reflector overlying said layer. of beads and thestruc-; ture of sai'cl reflex-reflector underlyingsaid layer of beadsf the structure overlying; saidQbeads[comprisingfarltrans parent biaxially-orientedniethyl methacrylate cover film; and the structurennderlying said beads comprising, a binder layer in which. said beads are partially embedded and internal light-reflecting means underlyings aid ibeads' and in optical connection with the backcxtremitiesth erea of, those beads of the sheeting in the intersecting grid pat:

tern oft pressure=formed Iheat-sealed. connection being-a flooded over and optically obscured by binderlayer ma: terial dipslaced from. said: binder layerand hermetically sealed to said transparentycover film, according to said in- JEWELL HQ PEDERSEN,-Primary Examiner, VEMIL G.. ANDERSON, Examiner. 7

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,190,178 June 22, 1965 Eugene L. McKenzie It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 25, for "2.0 maximum" read 2.0 for maximum line 34, for "angle" read angles line 55, for "protometer" read photometer column 2, line 10, for "contact at" read contact air at line 21, for "shaps" read shapes line 58, for "air-interference" read air-interface line 61, for "in" read is column 3, line 15, for "its" read it line 66, for "interesting" read intersecting column 5, line 45, for "extending" read extruding column 7, line 34, for "reflux-reflecting" read reflex-reflecting column 12,

line 29, for "dipslaced" read displaced Signed and sealed this 29th day of November 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. REFLEX-REFLECTING SHEETING COMPRISINNG A CONTINUOUS LAYER OF GLASS BEADS IN COMPACT REALTIONSHIP TO ONE ANOTHER, AND MEANS SEPARATING SAID LAYER OF BEADS INTO A PLURALITY OF DISCRETE ENCAPSULATED AND HERMETICALLY SEALED POCKETS HAVING NO LATERAL DIMENSION GREATER THAN THREEFOURTHS INCH, WITH THE BEADS OF EACH SAID DISCRETE POCKET OPTICALLY EXPOSED TO AN AIR INTERFACE, SAID SEPARATING MEANS BEING RELATIVELY SMALL IN TOTAL AREA AS COMPARED TO THE TOTAL AREA OF SAID POCKETS, AND SAID SEPARATING MEANS INCLUDING AN INTERSECTING GRI PATTERN OF PRESSURE-FORMED HEAT-SEALED CONNECTION BETWEEN THE STRUCTURE OF SAID REFLEX-REFLECTOR OVERLYING SAID LAYER OF BEADS AND THE STRUCTURE OF SAID REFLEX-REFLECTOR UNDERLYING SAID LAYER OF BEADS, THE STRUCTURE OVERLYING SAID BEADS COMPRISING A TRANSPARENT COVER FILM, AND THE STRUCTURE UNDERLYING SAID BEADS COMPRISING A BINDER LAYER IN WHICH SAID BEADS ARE PARTIALLY EMBEDDED AND INTERNAL LIGHT-REFLECTING MEANS UNDERLYING SAID BEADS AND IN OPTICAL CONNECTION WITH THE BACK EXTREMITIES THEREOF, THOSE BEADS OF THE SHEETING IN THE INTERSECTING GRID PATTERN OF PRESSURE-FORMED HEAT-SEALED CONNECTION BEING FLOODED OVER AND OPTICALLY OBSCURED BY BINDER LAYER MATERIAL DISPLACED FROM SAID BINDER LAYER AND HERMETICALLY SEALED TO SAD TRANSPARENT COVER FILM ACCORDING TO SAID INTERSECTING GRID PATTERN. 